Brandishing Iraqi flags and portraits of "martyrs", they marched to Tahrir Square, an epicentre of the 2019 revolt, surrounded by a large number of riot police, AFP correspondents said.

"When will we see the killers behind bars?" and "No to corrupt parties, no to corrupt politicians," said placards carried by the demonstrators who included women dressed in black.

On October 1, 2019, widespread rallies erupted across Baghdad and the south of the country against a government seen as corrupt, inept and beholden to Iran.

Protest-related violence killed nearly 600 people, including some shot dead while walking home from demonstrations.

Saturday's rallies come just ahead of Iraq's October 10 parliamentary election, one of the few concessions offered by the government to calm the unrest of 2019.

One of those taking part, Ibrahim, said he was doing so "in memory of the martyrs" and "the massacres committed by the government against young pacifists".

The 20-year-old, who like many Iraqis prefers not to give his full name when discussing politics, said he would not vote.

"The election will reproduce the same corrupt system, and the same corrupt parties. Only the names and faces change," he said.

The 2019 protests that saw tens of thousands camp out in Tahrir eventually withered in the face of the crackdown and the onset of the coronavirus pandemic.

Dozens of activists have died in targeted killings or been abducted since October 2019, in attacks normally carried out in the dead of night by men on motorbikes.

Nobody has claimed responsibility, but the protesters point the finger at powerful pro-Iranian militias linked to the Iraqi government.

Activists and parties claiming to be part of the uprising are boycotting the election, with observers predicting a record low turnout among the 25 million voters.

A new electoral law increased the number of constituencies and opted for a single-member constituency system supposed to favour independents and community-based candidates.

But experts say the same major political blocs are likely to dominate the next parliament.

On Friday, however, some showed optimism.

"The revolution will spread through the country faster than the coronavirus, and there is no vaccine," read one placard at the Baghdad rally.